The 41-year-old actress recently enjoyed a "girls trip" to Napa Valley in California with Drew Barrymore and Reese Witherspoon. They took a cooking class together at the Culinary Institute of America in St Helena, reported OK! magazine.
"I exist for all my girlfriends. I am very, very, very fortunate, my friends are incredible and I am very lucky to have a lot of really solid, good friends," Diaz said.
The 'Bad Teacher' star, who is very health conscious, released her first publication, 'The Body Book' in December last year.
The actress had previously said that she was inspired by Gwyneth Paltrow and Drew, who too had penned some books in the past.